1. Field of the Invention
The invention relates to an acceleration-sensitive locking device and more particularly to a safety belt retractor locking device responsive to vehicle acceleration, of the type including a rollable, freely movable inertia member supported in a depression by a supporting member, and a pawl disposed above the inertia member and engageable with a locking wheel, the pawl being provided with a depression facing the inertia member.
2. Description of the Prior Art
A similar belt retractor with a locking device, disclosed in U.S. Pat. No. 3,901,461, contains as the inertia member a freely movable sphere supported in a depression, the surface of the sphere being in contact with a depression-containing extension of a locking wheel. In the event of an accident, in which the vehicle and, hence, the belt retractor is subjected to impact, the sphere moves relative to the depressions thereby pressing the pawl into engagement with the locking wheel.
Many other inertia members are also known which contain a pendulum responsive to changes in velocity. In all these belt retractors, the pawl-engaging process frequently is too slow, because the pawl enters the opening between the two teeth of the locking wheel too slowly. The time needed for the engaging process to occur is frequently similar in length to the time needed by the locking wheel to advance the distance of one tooth. In this manner, the pawl can skip over the locking wheel in ratchetlike fashion without entering into locking engagement, thus markedly decreasing reliability.
The known locking devices of this type have the drawback that they either have excessive space requirements or they do not provide enough freedom of movement for the inertia member which, for example, is spherical in shape. Most known devices also show an undesirable dependence on the character of the surface on which the sphere rolls or in which the pendulum-supporting member swings.
It would be desirable to eliminate these drawbacks by improving the locking device of the aforementioned type by minimizing the zone of uncertain engagement between the pawl and the locking wheel, providing a favorable locking position quickly and then ensuring the quick return of the inertia member to its rest position, wherein the pawl is out of engagement with the locking wheel, without expensive surface treatment of the support member.